(Received 27 October 2012;accepted 30 October 2012;online 7 November 2012)

In the title hydrate, C13H11N3O·H2O, the benzotriazole ring system is planar (r.m.s. deviation = 0.007 Å) and is almost orthogonal to the phenyl ring to which it is linked by a methyl­ene group, forming a dihedral angle of 81.87 (15)°. In the crystal, mol­ecules are linked into chains along [001] by O—H⋯O hydrogen bonds. The chains are consolidated into a three-dimensional architecture by C—H⋯O, C—H⋯π and π–π [centroid–centroid distance between the five- and six-membered rings of the benzotriazole ring system = 3.595 (3) Å] inter­actions.

Benzotriazole derivatives show biological activities such as anti-inflammatory, diuretic, anti-viral and anti-hypertensive (Kopańska et al., 2005; Sarala et al., 2007). They have been used as a corrosion inhibitor, anti-freeze agent, ultraviolet light stabilizer for plastics and as an anti-foggant in photography (Krawczyk & Gdaniec, 2005; Smith et al., 2001). N-aryloxy derivatives of benzotriazole have anti-mycobacterial activity (Kopec et al., 2008). Benzotriazole possessing three vicinal N atoms, is used as an anti-fouling and anti-wear reagent (Sha et al., 1996). Due to the above mentioned applications of benzotriazole, we have systematically synthesised and investigated the structures of novel benzotriazole derivatives. We have already reported the crystal structure of 1-(benzyl)-1H-benzotriazole (Selvarathy Grace et al., 2012). Here, we report the crystal structure of the title compound (I).

The benzotriazole ring in (I), Fig 1, is essentially planar with the maximum deviation from planarity being 0.010 (3) Å for atom N3. The mean plane of the benzotriazole ring (N1–N3,C4–C9) forms a dihedral angle of 81.87 (15) Å with the mean plane of the phenyl ring (C11–C16).

The molecules are linked into a one dimensional chain along [001] by O—H···O hydrogen bonds, Table 1 and Fig. 2. The crystal packing is stabilized by π–π stacking interactions with the centroid-centroid distance of 3.595 (3) Å [symmetry code: x, y, -1+z], together with C—H···O and C—H···π interactions, Table 1.

A mixture of sodium salt of 1-hydroxyl benzotriazole (0.157 g, 1 mmol) and benzyl chloride (0.126 g, 1 mmol) in a mixture comprising ethanol, water and sodium ethoxide (10 ml) were heated at 333 K with continuous stirring for 6 h. The mixture was kept aside for slow evaporation. After a week, crystals suitable for X-ray diffraction were obtained.

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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